My own prophecy about Minolta coatings come true - yesterday I started work on two Minolta MC lenses. A 35mm HG 2.8 and a 58mm PF 1.4. The 35 was an oddball as its guts are similar but not identical to an SR Auto Rokkor but the barrel and some of the interior is more like an MCII but not quite. Its neither wholly MCI or MCII. Simple to fix as these things are a horror for oiling up the apertures. That bit was easy but the lens faces were badly contaminated and nothing seems to make them really good. They look fine to the naked eye but put a torch on it and it looks bad. I have put this aside for further investigation.
All day today, and most of yesterday too, I have been hard at it with the 58mm. Its been a complete nightmare- like the Pentax lens in my 'HELP' thread it looked like it had been in a ditch for the past few years. Everything was either gummed with oil or covered in filth. I have had to take it back almost to its molecules to get it back together. Anti-reflection. coating on the back surface of the front lens (which according to what I read is a magnesium base) had been partly eaten away and the IPA reacted badly with the rest of it. Had to be cleaned off with acetone to remove what was left. So.....acetone will quite deffo remove a Minolta coating (that kiddies is your lesson for today
) its only taken maybe 6 hours to get the front element clean and looking good. Every element has been dosed with peroxide and IPA and polished, all the interior elements were hazed with what I assume to have been dried oil plus some fungus happily eating things. Aperture soaked off in IPA, focus helicoids cleaned out with methalyated spirits and the all other parts left in hot soapy water with commercial washing powder with bleaching agents in - as this lens is never going to be great I have chosen to use it as a test vehicle for some processes hence the washing powder which should annihilate fungal spores - we'll see. Its then been washed out with clear water, lenses washed with distilled water, left to try, all surfaces polished to perfection and then reassembled, helicoids greased and aperture ring cleaned out.
I never get round to taking many pics as I tend to get absorbed in what I am doing (I suffer mild OCD and it can be a bugbear times - on the other hand it leads to perfection often).
Anyway just finished this -how Ismael find the time to do this as often as he does baffles me. This lens has pretty much had a whole solid two days of work put into it and I am now exhausted not even eaten all day.
Heres some pics of it in pieces and one of the finished product - when I started yesterday looking through it was like looking through frosted glass smeared with oil, focus was jammed and the aperture non-reactive plus the aperture ring was jamming at fully closed and fully open.